On the video monitor, two small marmosets  tree-dwelling South American monkeys with white ear tufts  cling tightly to each other, looking terrified. A third writhes in pain, postsurgery, on the floor of its cage; others have raw and bloody head wounds that seem crudely stitched up. The animals appear in a 21-minute exposé called Cutting Edge, shot for the British Union for the Abolition of Vivisection (BUAV) in one of Cambridge University's neuroscience research labs. The monkeys' brains had been deliberately damaged in experiments meant to simulate the symptoms of stroke and Parkinson's disease. Important research that could help...